A known ultrasonic probe used for an ultrasonic diagnostic apparatus has an ultrasonic element for transmitting and receiving ultrasonic waves, and oscillates the ultrasonic element in a housing part filled with an acoustical coupling medium. The acoustical coupling medium has an acoustic impedance similar to that of living organisms. Such an ultrasonic probe is, for example, described in JP 6(1994)-038962A.
FIG. 5 is a cross-sectional view of the configuration of a conventional ultrasonic probe. The ultrasonic probe 20 is connected to an ultrasonic diagnostic apparatus (not shown in the figure) via a cable 25. The ultrasonic probe 20 has a housing 21 that is composed of an upper case 22 and a lower case 24 and includes a partitioning film 23 therein. In the space enclosed by the partitioning film 23 and the lower case 24, an acoustical coupling medium 27 is sealed. In the housing 21, an element part 26 is provided so that a portion for transmitting and receiving ultrasonic waves can be set in the acoustical coupling medium 27. In addition, an oscillation mechanism part 29 is equipped in the housing 21 for oscillating the element part 26. As shown in the figure, a rotation center 28 for the oscillation of the element part 21 is positioned at the center of a living organism contact barrier 24A forming an apex of the lower case 24. Moreover, a relay cable (not show in the figure) is connected to the element part 26 so as to draw a signal line from the element part 26. The relay cable is electrically connected to a cable 25, and signals received by the element part 26 can be input into the ultrasonic diagnostic apparatus via the cable. In the conventional ultrasonic probe, however, the relay cable is positioned at a distance from the central axis of the oscillation of the element part, leading to problems such as the incremental change in the drawing length of the relay cable and frequent bending and breaking of the relay cable with the oscillation of the element part.